One specific embodiment of the camshaft adjusting device proven in practice includes a vane cell adjuster with a stator and a rotor, which delimit an annular space, which is subdivided by projections and vanes into multiple working chambers. The working chambers may be selectively acted upon by a pressure medium, which is fed in a pressure medium circuit via a pressure medium pump from a pressure medium reservoir into the working chambers on one side of the vanes of the rotor and is fed from the working chambers on the respective other side of the vanes back to the pressure medium reservoir. The working chambers, the volume of which is increased in the process, exhibit an operating direction which is opposite the operating direction of the working chambers, the volume of which is reduced. Accordingly, the operating direction means that a pressure medium acting upon each group of working chambers causes the rotor to rotate either clockwise or counterclockwise relative to the stator. The pressure medium flow, and therefore the adjusting movement, is controlled, for example, with the aid of a central valve having a complex structure of flow-through openings and control edges and a valve body displaceable in the central valve, which closes or unblocks the flow-through openings as a function of its position.
One problem with such camshaft adjusting devices is that in a start phase they are not yet completely filled with pressure medium and may even be run dry, so that the rotor may carry out uncontrolled movements relative to the stator due to the alternating torques exerted by the camshaft, which may result in increased wear and an undesirable noise generation. To avoid this problem, it is known to provide a locking device between the rotor and the stator, which locks the rotor in a rotation angle position relative to the stator favorable for starting when the internal combustion engine is turned off. In exceptional cases, however, for example, when the internal combustion engine stalls, it is possible that the locking device does not lock the rotor as intended, and it is necessary to operate the camshaft adjuster in the subsequent start phase with an unlocked rotor. However, since some internal combustion engines have a very poor start behavior when the rotor is not locked in the center position, the rotor must then be automatically rotated and locked in the center locking position in the start phase.
Such an automatic rotation and locking of the rotor relative to the stator is known, for example, from DE 10 2008 011 915 A1 and from DE 10 2005 011 916 A1. The locking devices described in both publications include a plurality of spring-loaded locking pins, which lock successively in locking slots provided on the sealing cover or on the stator when the rotor is rotated and, in the process, allow the rotor in each case to rotate in the direction of the center locking position before reaching the center locking position, but which block a rotation of the rotor in the opposite direction. After the internal combustion engine is warmed up and/or the camshaft adjuster is filled completely with pressure medium, the locking pins, activated by the pressure medium, are forced out of the locking slots so that the rotor may be subsequently rotated as intended for adjusting the rotation angle position of the camshaft relative to the stator.
One disadvantage of this approach is that the rotor can be locked only with multiple successively locking locking pins, which results in higher costs. In addition, the locking process presupposes that the locking pins lock successively in a functionally reliable manner. If one of the locking pins fails to lock, the locking process may be interrupted, since the rotor is therefore not locked on one side in the intermediate position and may rotate back. In addition, it must be ensured that the locking pins may be reliably forced out of the locking slots during a start of the internal combustion engine.